This study will evaluate a new chemotherapeutic drug, Topotecan, in patients with advanced and previously treated AIDS-related Kaposi's sarcoma. This open-label study will determine the tolerance and anti- tumor activity of topotecan given by 21-day continuous infusion every 28 days. Eligible patients will be enrolled in tow stages. If there is no tumor response observed in the first 11 evaluable patients, the study will be terminated. Otherwise, 29 additional patients will be enrolled for determination of response rate, time to response, and duration.